The science we rely on to tell us what to eat is 'fatally flawed'

Alison Faith on Flickr
For decades, the federal government has been advising Americans on what to eat. Those recommendations have been subject to the shifting sands of dietary science. And have those sands ever been shifting.

At first, fat and cholesterol were vilified, while sugar was mostly let off the hook. Now, fat is fine (saturated fat is still evil, though), cholesterol is back, and sugar is the new bogeyman.

Why the sizable shift? The answer may be "bad science."

Every five years, the Dietary Guidelines Advisory Committee, composed of nutrition and health experts from around the country, convenes to review the latest scientific and medical literature. From their learned dissection, they form the dietary guidelines.

But according to a new editorial published in Mayo Clinic Proceedings, much of the science they review is fundamentally flawed. Unlike experiments in the hard sciences of chemistry, physics, and biology, which rely on direct observational evidence, most diet studies are based on self-reported data.

Study subjects are examined for height, weight, and health, then are questioned about what they eat. Their dietary choices are subsequently linked to health outcomes -- cancer, mortality, heart disease, etc.

That's a poor way of doing science, says Edward Archer, a research fellow with the Nutrition Obesity Research Center at the University of Alabama, and lead author of the report.

"The assumption that human memory can provide accurate or precise reproductions of past ingestive behavior is indisputably false,"

"The assumption that human memory can provide accurate or precise reproductions of past ingestive behavior is indisputably false."

he and his co-authors write.

Two of the largest studies on nutritional intake in the United States, the CDC's NHANES and "What We Eat," are based on asking subjects to recall precisely what and how much they usually eat.

But despite all of the steps that NHANES examiners take to aid recall, such as limiting the recall period to the previous 24 hours and even offering subjects measuring guides to help them report accurate data, the information received is wildly inaccurate.

An analysis conducted by Archer in 2013 found that most of the 60,000+ NHANES subjects report eating a lower amount of calories than they would physiologically need to survive, let alone to put on all the weight that Americans have in the past few decades.

So self-reported data based on memory recall is inaccurate, but that should come as no surprise to anyone familiar with how memory works.

Memory is not a recording; it's a mental reconstruction shaped by thoughts, feelings, and everything that occurred after the event one is trying to remember. Everybody is susceptible to false memories.

And yet, again, much of epidemiological dietary research is based on asking subjects to recall the easily altered details of what they ate! No wonder seems to point every which way!

Shutterstock
"The American public deserves the best possible science. It is time to stop spending billions of health research dollars collecting pseudoscientific, anecdotal data that are essentially meaningless," Archer said in a press release.

Diet studies based on self-report are conducted because they are easy. But in this case, what's easy is not at all better. Sure, the scientific literature on nutrition is bulging with studies, but at the same time, it's watered-down with weak, meaningless information. Perhaps that's why nutrition has become rife with hucksterism.

"The greatest obstacle to scientific progress is not ignorance but the illusion of knowledge created by pseudoscientific data that are neither right nor wrong," Archer writes.

Instead of focusing on inaccurate dietary advice, Archer urges a renewed focus on p hysical activity as a tool for maintaining health.

Nutrition research is awash in woo. To fix that, scientists should conduct only the most rigorous studies, preferably randomized-controlled trials, and funding agencies like the NIH and the CDC should only give grants to this sort of research.

The motto of the Royal Society of London, the oldest scientific society in the modern world, isNullius in Verba.

"This phrase... is translated as "on the word of no one" or "take no one's word for it" and suggests that scientific knowledge should be based not on authority, rhetoric, or mere words but on objective evidence," Archer writes.

Ironically, self-reported data directly contradicts the Royal Society's motto. Credulous nutrition scientists are literally taking everyone at their word. This has to end.